NAME: HIMANSHU NAME: HIMANSHU AGGARWALAGGARWAL

CLASS: VIIIth CLASS: VIIIth ROLL NO: 10ROLL NO: 10

NORTH EX PUBLIC SCHOOLNORTH EX PUBLIC SCHOOL

SOLAR SYSTEM

The Solar System[a] consists of the Sun and the astronomical objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. Of the many objects that orbit the Sun, most of the mass is contained within eight relatively solitary planets[e]

 whose orbits are almost circular and lie within a nearly flat disc called the ecliptic plane. The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, the gas giants, are substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are composed largely of ices, such as water, ammonia and methane, and are often referred to separately as "ice giants".

SOLAR SYSTEM DEFINTION

Discovery and Discovery and explorationexploration

many thousands of years, humanity, with a few notable many thousands of years, humanity, with a few notable exceptions, did not recognize the existence of the Solar exceptions, did not recognize the existence of the Solar

System. People believed the Earth to be stationary at the System. People believed the Earth to be stationary at the center of the center of the universe and categorically different from the  and categorically different from the

divine or ethereal objects that moved through the sky. divine or ethereal objects that moved through the sky. Although the Although the Greek philosopher  philosopher Aristarchus of Samos had  had speculated on a heliocentric reordering of the cosmos,speculated on a heliocentric reordering of the cosmos,[1]  

Nicolaus Copernicus was the first to develop a  was the first to develop a mathematically predictive mathematically predictive heliocentric system. system.[2] His 17th- His 17th-century successors, century successors, Galileo Galilei,,Johannes Kepler and  and 

Isaac Newton, developed an understanding of , developed an understanding of physics that  that led to the gradual acceptance of the idea that the Earth led to the gradual acceptance of the idea that the Earth

moves around the Sun and that the planets are governed by moves around the Sun and that the planets are governed by the same physical laws that governed the Earth. In more the same physical laws that governed the Earth. In more

recent times, improvements in the telescope and the use of recent times, improvements in the telescope and the use of unmanned spacecraft have enabled the investigation of  have enabled the investigation of

geological phenomena such as geological phenomena such as mountains and  and craters, and , and seasonal meteorological phenomena such as seasonal meteorological phenomena such as clouds, , 

dust storms and  and ice caps on the other planets. on the other planets.

STRUCTURESTRUCTURE

The principal component of the Solar System is the Sun, a main sequence G2 star that contains 99.86 percent of the system's known mass and dominates it gravitationally.[3] The Sun's four largest orbiting bodies, the gas giants, account for 99 percent of the remaining mass, with Jupiter and Saturn together comprising more than 90 percent.[c]

Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic. The planets are very close to the ecliptic while comets and Kuiper belt objects are frequently at significantly greater angles to it.[4][5] All the planets and most other objects orbit the Sun in the same direction that the Sun is rotating (counter-clockwise, as viewed from above the Sun's north pole). For exceptions, seeretrograde motion.

SUN SUN • The Sun is the Solar System's The Sun is the Solar System's star, and by far its chief , and by far its chief

component. Its large mass (332,900 Earth masses)component. Its large mass (332,900 Earth masses)[13] produces  produces temperatures and densities in its temperatures and densities in its core great enough to sustain  great enough to sustain nuclear fusion,,[14] which releases enormous amounts of  which releases enormous amounts of energy, , mostly mostly radiated into  into space as aselectromagnetic radiation, , peaking in the 400–700 nm band we call peaking in the 400–700 nm band we call visible light..[15]

• The Sun is classified as a type G2 The Sun is classified as a type G2 yellow dwarf, but this name , but this name is misleading as, compared to the majority of stars in is misleading as, compared to the majority of stars in our galaxy, the Sun is rather large and bright., the Sun is rather large and bright.[16] Stars are  Stars are classified by the classified by the Hertzsprung–Russell diagram, a graph that , a graph that plots the brightness of stars with their surfaceplots the brightness of stars with their surfacetemperatures. . Generally, hotter stars are brighter. Stars following this pattern Generally, hotter stars are brighter. Stars following this pattern are said to be on the are said to be on the main sequence, and the Sun lies right in , and the Sun lies right in the middle of it. However, stars brighter and hotter than the the middle of it. However, stars brighter and hotter than the Sun are rare, while substantially dimmer and cooler stars, Sun are rare, while substantially dimmer and cooler stars, known as known as red dwarfs, are common, making up 85 percent of , are common, making up 85 percent of the stars in the galaxy.the stars in the galaxy.[16][17]

Inner Solar SystemInner Solar SystemThe inner Solar System is the The inner Solar System is the traditional name for the region traditional name for the region comprising the terrestrial planets comprising the terrestrial planets and asteroids.and asteroids.[31] Composed mainly  Composed mainly of of silicates and metals, the objects  and metals, the objects of the inner Solar System are of the inner Solar System are relatively close to the Sun; the relatively close to the Sun; the radius of this entire region is radius of this entire region is shorter than the distance between shorter than the distance between Jupiter and Saturn.Jupiter and Saturn.

INNER PLANETS

• The four inner or terrestrial planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely ofrefractory minerals, such as the silicates, which form their crusts and mantles, and metals such as iron and nickel, which form their cores. Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial enough to generate weather; all have impact cratersand tectonic surface features such as rift valleys and volcanoes. The term inner planet should not be confused with inferior planet, which designates those planets that are closer to the Sun than Earth is (i.e. Mercury and Venus).

•

Mercury (0.4 AU from the Sun) is the closest planet to the Sun and the smallest planet in the Solar System (0.055 Earth masses). Mercury has no natural satellites, and its only known geological features besides impact craters are lobed ridges or rupes, probably produced by a period of contraction early in its history.[32] Mercury's almost negligible atmosphere consists of atoms blasted off its surface by the solar wind.[33] Its relatively large iron core and thin mantle have not yet been adequately explained. Hypotheses include that its outer layers were stripped off by a giant impact, and that it was prevented from fully accreting by the young Sun's energy.[34][35]

MercuryMercury

Venus• Venus (0.7 AU from the Sun) is close in size to Earth (0.815

Earth masses), and, like Earth, has a thick silicate mantle around an iron core, a substantial atmosphere and evidence of internal geological activity. However, it is much drier than Earth and its atmosphere is ninety times as dense. Venus has no natural satellites. It is the hottest planet, with surface temperatures over 400 °C, most likely due to the amount of greenhouse gases in the atmosphere.[36] No definitive evidence of current geological activity has been detected on Venus, but it has no magnetic field that would prevent depletion of its substantial atmosphere, which suggests that its atmosphere is regularly replenished by volcanic eruptions.[3

EarthEarth• Earth (1 AU from the Sun) is the largest  (1 AU from the Sun) is the largest

and densest of the inner planets, the only and densest of the inner planets, the only one known to have current geological one known to have current geological activity, and is the only place in the activity, and is the only place in the universe where  where life is known to exist. is known to exist.[38] Its  Its liquid liquid hydrosphere is unique among the  is unique among the terrestrial planets, and it is also the only terrestrial planets, and it is also the only planet where planet where plate tectonics has been  has been observed. Earth's atmosphere is radically observed. Earth's atmosphere is radically different from those of the other planets, different from those of the other planets, having been altered by the presence of life having been altered by the presence of life to contain 21% free to contain 21% free oxygen..[39] It has one  It has one natural satellite, the Moon, the only large natural satellite, the Moon, the only large satellite of a terrestrial planet in the Solar satellite of a terrestrial planet in the Solar System.System.

Outer Solar SystemOuter Solar System

The outer region of the Solar System is home to The outer region of the Solar System is home to the gas giants and their large moons. Many the gas giants and their large moons. Many short period comets, including the centaurs, short period comets, including the centaurs, also orbit in this region. Due to their greater also orbit in this region. Due to their greater distance from the Sun, the solid objects in distance from the Sun, the solid objects in the outer Solar System contain a higher the outer Solar System contain a higher proportion of volatiles such as water, proportion of volatiles such as water, ammonia and methane, than the rocky ammonia and methane, than the rocky denizens of the inner Solar System, as the denizens of the inner Solar System, as the colder temperatures allow these compounds colder temperatures allow these compounds to remain solid.to remain solid.

OUTER PLANETSOUTER PLANETS The four outer planets, or gas giants (sometimes called

Jovian planets), collectively make up 99 percent of the mass known to orbit the Sun.[c] Jupiter and Saturn are each many tens of times the mass of the Earth and consist overwhelmingly of hydrogen and helium; Uranus and Neptune are far less massive (<20 Earth masses) and possess more ices in their makeup. For these reasons, some astronomers suggest they belong in their own category, “ice giants.”[54] All four gas giants have rings, although only Saturn's ring system is easily observed from Earth. The term outer planet should not be confused with superior planet, which designates planets outside Earth's orbit and thus includes both the outer planets and Mars.